Could this resistor be cooked?

Thread Starter

circuit-tinkerer

Joined May 23, 2020
8
Could this resistor be cooked?
If anyone else thinks it looks suspect then ill unsolder an end and check.
Its near the mains power input of a PoE adapter that seems to run for a second before the LEDs just wink out.
All the electrolytic caps checked out ok with an ESR meter.
Am otherwise scratching around for the fault.
Thanks.
The Tinkerer.
PS is that 100 ohms?
 

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sagor

Joined Mar 10, 2019
439
Based on the pictures, it does not look burnt. The color bars are still readable, and color seems correct for a 100 ohm resistor.
Many faults near the input can be a fusible link of some sort, or a blown MOV which blows the fuse.
EDIT: That orange/reddish thing at upper left may be a fuse of some sort, based on what text I can read on it ("...A 250V")
 

sagor

Joined Mar 10, 2019
439
Usually if a fuse reads ok, it is ok. It could be a thermal reset type of fuse. That is, it trips when overloaded and then resets. The fact you describe "it runs for a second , then trips", suggests some overload elsewhere. A shorted diode perhaps? ANything on the output side that could be shorted, like a MOV/thyristor?
 

Thread Starter

circuit-tinkerer

Joined May 23, 2020
8
thanks, there is something that looks like an MOV but it looks OK. Lots of diodes too including surface mounted ones - can they be tested in-circuit?
 

DickCappels

Joined Aug 21, 2008
7,426
Testing diodes in-circuit. Using a digital multimeter in the diode test mode, check for shorted diodes. Open diodes might be hard to detect but they are less likely to be a problem.
 
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